In recent years, a vehicle mounted with a hybrid system and an idling stop system has been developed based on concerns of environmental protection. Such systems perform operations such as regenerating a braking energy of a vehicle as an electrical energy and driving a high output motor, and thus a configuration of temporarily accumulating the electrical energy in a power accumulating element is necessary.
FIG. 47 is a perspective view of a conventional battery unit. In FIG. 47, the battery unit includes plural batteries 1 having electrodes at both end faces, and bus bars 3, which are made of plate-shaped metal, for electrically connecting plural batteries 1. Bus bars 3 are alternately arranged at both ends of plural batteries 1, so that plural batteries 1 connected by bus bars 3 are connected in plural stages and laid in a horizontal direction. Insulation sheets 5 are arranged to prevent short-circuit between each stage.
According to such a configuration, the battery unit accumulates the electrical energy in the battery at normal times, and supplies power to an information processing device when a power supply source shows abnormality due to blackout and the like. The battery unit that accumulates the electrical energy in the battery and backs up the information processing device is disclosed in patent document 1.
The conventional battery unit backs up the necessary power to the information processing device and the like in time of black out, and prevents the system down.
However, in the regeneration system of the vehicle, the braking energy that suddenly changes needs to be accumulated in the power accumulating element as the electrical energy, and the electrical energy for rapidly accelerating the vehicle needs to be supplied in assisting the motor drive. Although rapid charging/discharging characteristics are demanded on the power accumulating element, battery 1 used as the power accumulating element of the conventional battery unit has poor rapid charging/discharging characteristics.
For the configuration using a capacitor enabling rapid charging/discharging in place of battery 1, the characteristic degradation may advance when the voltage value between both ends of the capacitor becomes higher than a predetermined value. Therefore, when using the capacitor, a voltage balance circuit for measuring and controlling the voltage value between both ends of each capacitor needs to be arranged. When applied to the conventional battery unit, bus bars 3 will be alternately arranged at both upper and lower end portions 7 of the capacitor, and thus a circuit substrate including the voltage balance circuit also needs to be arranged at both upper and lower end portions 7 of the capacitor, and as a result, the capacitor unit becomes larger and heavier.    [Patent document 1] Unexamined Japanese Patent Publication No. 2003-309935